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Diaries and writings from ninth-century Baghdad provide a glimpse of the weird weather from the era, findings that could help researchers reconstruct past climate.

The surviving documents were written by historians and scholars during the Islamic Golden Age between A.D. 816 and A.D. 1009. They provide a new human record of climate, joining old ship's logs and World War II air force reports as one of the few sources for detailed information on historical weather.

"Climate information recovered from these ancient sources mainly refers to extreme events which impacted wider society, such as droughts and floods," study researcher Fernando Dominguez-Castro of the University of Extremadura in Spain said in a statement. "However, they also document conditions which were rarely experienced in ancient Baghdad such as hailstorms, the freezing of rivers or even cases of snow."

Many of the writings from the Islamic Golden Age have been lost in wars and upheaval. But some works survive, including those of Sunni scholar al-Tabari (A.D. 913), Kurdish historian Ibn al-Athir (A.D. 1233) and Egyptian scholar al-Suyuti (A.D. 1505).

Dominguez-Castro and his colleagues collected and analyzed these documents and found that they revealed a pattern of increasing frequency of cold-weather events in the early 10th century. July A.D. 920 was unusually cold, perhaps because of a volcanic eruption, Dominguez-Castro said. It snowed in Baghdad in 908, 944 and 1007. The only snow in living memory in the city was in 2008.

The findings suggest that Iraq's climate was more prone to unusually chilly events than it is today.

"Ancient Arabic documentary sources are a very useful tool for finding eyewitness descriptions which support the theories made by climate models," said Dominguez-Castro. "The ability to reconstruct past climates provides us with useful historical context for understanding our own climate."